This application details a two-part, five year research career development program in bacterial pathogenesis. The program will be conducted under the guidance of Dr. Stephen B. Calderwood, Division of Infectious Diseases, Massachusetts General Hospital, Boston, MA. The candidate is trained in Infectious Diseases and has the long-term career goals of gaining expertise in bacterial pathogenesis, with special emphasis on gene regulation. The program will include sessions of instruction in laboratory techniques and courses in microbiology and molecular genetics at Harvard Medical School. The research component of the program will focus on transcriptional regulation of virulence genes in Vibrio cholerae in response to environmental signals. V. cholerae is a well-studied model for bacterial pathogenesis and gene regulation. One operon of regulatory genes in V. cholerae, tcpPH, is regulated at the transcriptional level by temperature and pH, and the project focuses on further characterization of this regulation. Three specific aims will be addressed: (1) to further investigate transcriptional regulation at the tcpPH promoter by environmental conditions in the two biotypes of V. cholerae, classical and El Tor; (2) to identify novel proteins necessary for regulation of tcpPH transcription by environmental signals in vitro; and (3) to find novel proteins which activate tcpPH transcription in response to the host environment during in vivo infection. The mentor and an advisory committee will oversee the applicant's progress and research. The program will allow the candidate to obtain the skills, knowledge, and experience to become an independent biomedical researcher in bacterial pathogenesis.